Evan McDonough
McGill University
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Publication
Featured researches published by Evan McDonough.
Journal of Cosmology and Astroparticle Physics | 2013
Yi-Fu Cai; Evan McDonough; Francis Duplessis; Robert H. Brandenberger
We re-examine the non-singular Matter Bounce scenario first developed in [20], which starts with a matter-dominated period of contraction and transitions into an Ekpyrotic phase of contraction. We consider both matter fields, the first of which plays the role of regular matter, and the second of which is responsible for the non-singular bounce. Since the dominant matter field is massive, the induced curvature fluctuations are initially not scale-invariant, whereas the fluctuations of the second scalar field (which are initially entropy fluctuations) are scale-invariant. We study the transfer of the initial entropy perturbations into curvature fluctuations in the matter-dominated phase of contraction and show that the latter become nearly scale invariant on large scales but are blue tilted on small scales. We study the evolution of both curvature and entropy fluctuations through the bounce, and show that both have a scale-invariant spectrum which is blue-tilted on small scales. However, we find that the entropy fluctuations have an amplitude that is much smaller than that of the curvature perturbations, due to gravitational amplification of curvature perturbations during the bounce phase.
Journal of High Energy Physics | 2014
Keshav Dasgupta; Rhiannon Gwyn; Evan McDonough; Mohammed Mia; Radu Tatar
A bstractWe revisit the classical theory of ten-dimensional two-derivative gravity coupled to fluxes, scalar fields, D-branes, anti D-branes and Orientifold-planes. We show that such set-ups do not give rise to a four-dimensional positive curvature spacetime with the isometries of de Sitter spacetime. We further argue that a de Sitter solution in type IIB theory may still be achieved if the higher-order curvature corrections are carefully controlled. Our analysis relies on the derivation of the de Sitter condition from an explicit background solution by going beyond the supergravity limit of type IIB theory. As such this also tells us how the background supersymmetry should be broken and under what conditions D-term uplifting can be realized with non self-dual fluxes.
Journal of Cosmology and Astroparticle Physics | 2016
Evan McDonough; Marco Scalisi
We develop a new class of supergravity cosmological models where inflation is induced by terms in the Kahler potential which mix a nilpotent superfield
Journal of Cosmology and Astroparticle Physics | 2016
Evan McDonough; Hossein Bazrafshan Moghaddam; Robert H. Brandenberger
S
Journal of Cosmology and Astroparticle Physics | 2013
Evan McDonough; Robert H. Brandenberger
with a chiral sector
Journal of High Energy Physics | 2015
Keshav Dasgupta; Maxim Emelin; Evan McDonough
\Phi
Physical Review D | 2015
Laurence Perreault Levasseur; Evan McDonough
. As the new terms are non-(anti)holomorphic, and hence cannot be removed by a Kahler transformation, these models are intrinsically Kahler potential driven. Such terms could arise for example due to a backreaction of an anti-D3 brane on the string theory bulk geometry. We show that this mechanism is very general and allows for a unified description of inflation and dark energy, with controllable SUSY breaking at the vacuum. When the internal geometry of the bulk field is hyperbolic, we prove that small perturbative Kahler corrections naturally lead to
Journal of Cosmology and Astroparticle Physics | 2018
Stephon Alexander; David N. Spergel; Evan McDonough
\alpha
Classical and Quantum Gravity | 2018
Hossein Bazrafshan Moghaddam; Ryo Namba; Evan McDonough; Robert H. Brandenberger
-attractor behaviour, with inflationary predictions in excellent agreement with the latest Planck data
Classical and Quantum Gravity | 2018
Stephon Alexander; Robert Sims; Evan McDonough; Nicolas Yunes
We study the preheating of gauge fields in a simple axion monodromy model and compute the induced entropy perturbations and their effect on the curvature fluctuations. We find that the correction to the spectrum of curvature perturbations has a blue spectrum with index